Process for softening water.



. principally employed. One precipitates the s A ns PATENT ormon.

ROBERT GANS, OF PANKOW, NEAR BERLIN, GERMANY, ASSIGNOR TO J. D. BIEDEL, AKTIENGESELLSCHAFT, OF BERLIN, GERMANY, A CORPORATION OF GERMANY.

. raocnss ron sor'rmvrne WATER.

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Pankow, near Berlin, Germany, haveinvented a certain new and useful'Process for Softening Water, of. which the following is I a specification.

For softenlng water two processes are lime and the magnesia in the water by the addition of lime and soda, the other by the addition of lime and baryta. Both processes suffer from the disadvantage that in the softening of cold water the precipitation of the lime and of the magnesia does not take place instantaneously, but only after acomparatively long time. It is also impossible to obtain complete softening by one of the said processes. These 4 disadvantages are avoided by the following rocess, which utilizes the property of zeo ites to absorb caustic lime or caustic baryta, and when brought into contact with the bicarbonates and sulfates of lime and of magnesia, to

give up to these salts the bases thus. absorbed. In this manner carbonates of lime,

magnesia-or baryta or sulfate of baryta are; formed and by theremoval ofthese bodies the hardness ofthe water disappears, Complete softening may also be obtained by the addition alone of lin're to zeolites, whereby the bicarbonates of lime and macgnesia are precipitated, if the water so treate be caused to pass through a supplemental filter of sodlum-zeolite, which converts also the sulfates, nitrates and chlorids of lime and mag-'- nesia into the corresponding sodium salts by exchange of the bases.

It is only necessary to take care, that the filter does not become. choked, by frequently stlrring up and skimming ofl? the precipititted lime magnesiaand baryta-salts. It is advantageous also to employ upward filtration, the fine-grained recipitatesbeing washed off out of the lter, after which filtration is performed in a second filter, for which purpose among others a sodiumzeolites of the second or supplemental filter, which by this process are gradually converted into calcium and magnesium-zeolites, are re-generated from time to' time by the addition of solutions of common salt.

In comparison with softening by zeolites alone the present process has the advantage;

Speeifieaticn ofLetters r tent; Application filed December 16, 1909. Serial 1%. 533,350.

The

Patented June 7, mic.-

that it partially employs cheaper reagents in v the form of lime, and that it permits of a considerably greater speed of filtration and consequently requires a smaller filtering sur- 1 face. In comparison with the lime-soda process the present process likewise offers very important advantages. It permits of the use of the cheapest precipitating and regenerating agents, namely caustic lime for hardness due to carbonate, and chlorid of sodium for hardness due to sulfates, in the regeneration of the zeolites. Furthermore the accurate proportioning of the lime in a dissolved form by the so-called lime saturator, as required by the lime-soda process,

is dispensed with, as the zeolites possess the hitherto unknown property of adding alkalinity and of giving it up again on contact with bicarbonates. In this case therefore the zeolites undertake the aforesaid proportioning, which otherwise is difficult to carry out on a commercial scale. In the lime-zeoliteprocess the separation of the lime takes lace almost instantaneously in the layer 0 the zeolite containing the free caustic lime, while in the lime-soda process a comparatively long time is necessary after the addition of the soda for completing the reaction, a circumstance which renders a larger plant (water reservoirs) necessary. The softening of the same quantities of water consequently necessitates according to the present process i a far smaller space than according to the known process. Finally complete softening to zero degree is not practicable with the lime-soda process, but may be obtained with the lime-zeolite process. c The effects obtained in the present process "by the alkaline earths can be obtained in the filtration of the water also by the continuous addition of the hydroxids and carbonates of alkalies. In this case also the zeolites undertakethe accurate proportioning, as they absorb the alkalinity in a manner similar to that of the alkaline earths and give itiup again to the bicarbonates of the water.

' Example 1: Water of 10 German degrees of hardness,viz.', water containing ten parts by weight of lime and magnesia in 100,000

(one hundred thousand) parts of water of which '9 degrees are caused by bicarbonates lime and 20 mg. of hydrate of baryta per liter and filtered at once through a comand 1 degree by other salts of the earth-alkalies, is' mixed with 130 mg. of hydrate of supplementary filter and converts theniverts the remaininglimeand'magnesia-salts into sodium salts. .Thesoftening is perfect.

. rinsing and regeneration by commonsalt.

-par atively thick layer of sodium zeolite. By this treatment perfect softening is obtained,

3 Example II: To the above water of 10 degrees of hardness are added 132 mg. of y as the lower layer of the zeolites acts as a trates, chlorids and undeoomposed' sulfatesof lime and magnesia still present into the corresponding sodium salts.

hydrate of lime and the water is filtered at once through. a layer of sodium zeolite, the filtration taking place from the bottom upward. In this filter is completed the con version of the bicarbonates of the lime and magnesia in the water into carbonates, which however, when the speed of filtration is high, pass through the layer of zeoliteand render the water turbid. To clarify this water it is filtered through a supplemental filter of sodium-zeolite, which at the'same time con- The supplemental filter requires frequent Example III: Water oflO German degrees of hardness receives per liter an addition of 190 milligrams of soda and is immediately, without waiting for the completion of the reaction filtered off through a layer of sodium zeo ite, the speed of filtration being 10 meters and more per hour.

ing it through zeolite, substantially as described.

. 2. The process for softening water, which consists in mixing the water with hydroxid of lime and filtering it through a sodiumzeolite, substantially as described.v

3. The process for softening water, which consists in mixing the water with the hydroxid of an alkaline earth, then filtering it through a layer of sodium-zeolite and finally passing it through a supplemental filter of sodium-zeolite, substantially as described.

In testimony whereof I have hereuntoset my hand in presence of two subscribing Witnesses.

I ROBERT GANS.

; Witnesses:

AUGUST NEUMANN,

CORNELIUS MAssAoIU. 

